Colour television picture tube



April 14, 1959 P. M; VAN ALPHEN ETAL 2882432 COLOUR TELEVISION PICTURE '1UBE Filed Jan. 17, 1956 2 Sheets-Sheet 1 PIETER MAR'IINUS VAN ALPHEN ADRIAAN GERARD VAN DOORN JAN CAREL FRAN.CKIN

BYW

AGT

April 14, 1959 P. M. VAN ALPHEN ETAL 32 QOLOUR TELEVISION PICTURE TUBE Filed. Jan. 1r, 1956 2 Sheets-Sheet 2 INVENTOR RM. VN ALPHEN AG. VAN.DOORN BY J.G. FRANG EN Uniteci Sttes Patent COLOUR TELEVISION PICTURE TUBE Pieter-Martinus van Alphen, Adriaan Gerard van Doorn,

and Jan Carel Francken, Eindhoven, Netherlands, assignors, by mesne assignments, to North Ameriean Philips Company, Ine. New York, N.Y., a corporation of Delaware Applieation January 17, 1956, Serial No. 559,719

Claims priority, application N etherlands January 19, 1955 Claims. (Cl. 3135-92) A eolour television picture tube is known, whieh eomprises a sereen provided with parallel, strip-shaped element lumineseing in relatively different eolours npon ex eitation by an electron beam and distributed in a eertain order of sueeession over the sereen. Sueh a tube produees, it is true, a eolour image, but sornetimes an observer gets the impression that the strip-shaped elements luminesce separately in different eolours. Then he does not get the impression of a uniformly coloured lumineseent image, but of a picture divided into strips of dlereht eolours. The present invention has for its object te obviate ths disadvantage.

In accordance with the invention, the eolour television picture tube of the aforesad kind has, to this end, the feature that on the observers side of the first sereen the tube eomprises a second sereen, whieh diiuses the passing light from the first sereen, however, substantially only in directions transverse to the drection of length of the strip shaped elements on the first sereen. It is found that this measure ean obviate the aforesaid disadvantage of the known tubes.

Aecordng to one aspect of the invention the second screen is provided with ribs extending parallel to the stripshaped elements on the first sereen. Aecordng to a further aspect of the invention these ribs operate preferably as eylinder lenses.

In accordance with the invention it is advsable to choose the transverse dimension of the ribs en the second sereen te be at a maximum equal to the transverse dimension of the strp-shaped elements on the first sereen. Partieularly satisfaetory results are obtained, if the second sereen is spaeed apart from the first sereen by a distanee whieh exceeds twice the foeal distanee of the eylinder lenses and whieh is preferably at least equal to tour times ths foeal distanee.

The invention will be deseribed more fully with referenee to the drawng, in whieh:

Fig. 1 is a sehematic view of the plural sereen structure of the picture tube of the invention;

Fig. 2 is a eross-seetional view of a picture tube with the new sereen structure.

Fig. 1 of the drawng shows a eross-seetion of the sereen 1 comprised in a eolour television picture tube: ths sereen is provided with parallel, strip-shaped elements, of whieh the drawng shows the elements 2, 3 and 4 in eross-seetion. These elements have the property that they, npon being struck by an electron bearn the drection of whieh is indieated by the arrows P, luminesce in diflerent eolours. These elements are distributed in a partieular order over the sereen and exhibit, in reality, an extremely small transverse dimension of about 0.1 mm. T his transverse dimension is designated in the drawng by a. Eaeh of these strip-shaped elements luminesees in one of three In order to red images to be deseribed hereinafter are designated by one vertieal dash, the blue element 3 and the blue images Patented Apr- 14, 1959 by two vertieal dashes andthe green element 4 andthe green images by three vertical dashes.

Ifan observer looks through the front side (not shown) of the tube, at the sereen 1, i.e. the sereen 20 beirig assumed to be omitted, he might observe the line structure of the image on the sereen subdivided into the three eolours. In order to obviate ths dsadvantage the observers side of the sereen 1, i.e. on the right-hand side of this sereen viewed in the drawng, is provided with means 20 inside the tube in order to diffuse the light emanating from the sereen 1, however, in a manner sueh that this diiuson takes plaee substantially onlyin directions transverse to the drection of length of the elements of the sereen 1. These light-diffusing means eonsist in the embodiment shown in the drawng of a series of straight, positive eylindreal lenses, of whieh the drawng shows.three, i.e. the lenses 5, 6 and 7. Consequehtly, they have a beam eiect in the plane of the drawng: they operate as planoparallel glass plates in planes at right angles to the Plane of the drawng through the optieal axes VV, VIVI and VII-VII respeetively.

In the embodment shown in the drawng. eaeh of these lenses has an operative height b in the plane of the drawing, this height being equal to the transverse dimension a of eaeh of the strip-shaped elements 2,3 and 4.

The arrangement of eaeh of the eylinder lenses 5, 6 and 7 with the foeal pints F F and F respeetively, elative to the strip-shaped elements 2, 3 and 4 is ehosen to be sueh that eaeh of the distanees of the objeets V V and V is equal to four times the assoeiated foeal distanee f f and f, respeetively. This results in image distanees b b and b respeetively, eaeh of which is 1% times the assoeiated focal distanee f f and f7 respeetively. Thus the eylinder lenses 5, 6 and 7 produee, in the plane of the drawng, reduced images 8, 9 and 10 of the parts of the seetion of the strip-shaped elements 2, 3 and 4 in front of the eylinder lenses. The height e of these images is, in the arrangement shown, /3 of the height of the stripshaped elements 2, 3 and 4.

Eaeh of the lenses 5, 6 and 7 produees, however, also a reduced real image of the adjaeent strip-shaped elements, these images lying approximately also in a distanee of 1% times the foeal distanee of the lenses on the righthand side thereof. The image of the element 3 produeed by the lens 5 is designated by 11, the image of the elements 2 and 4 produeed by the lens 6 by 12 and 14 respeetively and the image of the element 3 prodneed by the lens 7 by 15. The images 16 and 17 produced by the lenses 5 and 7 respeetively emanate from elements of the sereen 1, whieh are not shown in the drawng and whieh are adjacent over the element 2 and below the element 4 respeetively.

Thus an observer does no longer see the eomparatively eoarse line structure with a height a of the elements 2, 3 and 4, but (in this case) a three times finer line structure, whieh ean hardly be eonsidered as a line structure. This improves materially the eolour image reproduetion.

Instead of using the positive eylinder lenses, use may be made of negative eylinder lenses; even prisms may produce the desired eieet.

The effect amed at may be improved further, if the height of the eylinder lenses is chosen not to be equal to the height a of the strip-shaped elements, but to be smaller.

The said sereen may be made of glass or of a synthetie substanee. Partieularly in the latter case it most be considered that the material of the sereen inside the tube must not give rise t0 phenomena whieh are likely to detraet from the quality of the tube.

Fig. 2 shows the sereens 1 and 20 in postion in the eathode-ray tube, whieh ineludes the usual electron gun 22 and defleetion coils 23 at the neek end of the tube. As

shown, the strip-shaped lumineseent elements 2, 3 and 4 3 are mounted en a light-transparent glass support 24, and the sereen 20 eomprisng the eylindrieal lenses 5, 6 and 7 is spaced therefrom the proper dstance te obtain the finer lnestrueture of the inventon.

What is elaimed is:

1. A eolor televsion picture tube eornprising, an electron-reeeiving sereen comprising a plurality of parallel, elongated, strip-shaped, eleetron-respnnsive, eolor-produeing areas with adjacent areas produeing dfierent eolored lght and with some areas produeing the Same colored light grouped in a periode manner on sad sereen, eleetron beam producing means on one side of sad sereen for exeting same, and a plurality of lentieular elements disposed en the side of sad sereen opposite to sad one side for elmnating the lne-like appearanee of the sereen, sad lentieular elements eooperatng with sad eolor-produeing areas to produee, in a transverse direetion t sad elongated areas, a plurality of images of eaeh elongated,

eoler-proclueing area on the side of sad lenticular ele- 4 areas and disposed en the side of sad sereen oppesite te sad one side for eliminating the line-like appearanee of the sereen, a lentieular element being assoeiated with eaeh of sad eolor-produeing areas, sad lentieular elements being spaeed from their assoeiated eolor-produeing area a dstanee greater than its foeal length and at whieh, in a transverse direetion te sad elongated areas, a plurality of images of eaeh eolor-produeing area are produeed on the side of sad lentieular elements remote frorn sad sereen, whereby the resultant maged line strueture has at least twiee the fineness of that of the eleetron-reeeivng sereen.

3. A picture tube as set forth in claim 2 wherein the width of the elongated lenticular element is not greater than the width of the strip-shaped area.

4. A picture tube as set forth in claim 3 wherein the spaeng between the lentieular elements and the colofproducing areas is at least twice the foeal length of the lentieular elements.

5. A picture tube as set forthin claim 4 wherein the sad spaeing is about OI1I' times the foeal length, thereby produeng three spaeed rnages of eaeh color-produeing area of the sereen.

References Cited in the file of ths patent UNITED STATES PATENTS 2337,980 Du Munt Dec. 28, 1943 2479,820 De Vore Aug. 23, 1949 2, 605,434 Homrighous July 29, 1952 2,682,571 Okoliesanyi June 29, 1954 

